Selection of conveyor roller
A conveyor roller is used to support the conveyor belt and the materials on the belt, reduce the working resistance of the conveyor belt, ensure that the sag of the conveyor belt does not exceed the technical rules, and make the conveyor belt work smoothly in the predetermined direction.
Roller according to its use is mainly divided into carrier roller, return roller, impact roller, and aligning roller. The roller is one of the key parts affecting the operation effect of the conveyor, accounting for about 30% ~ 40% of the quality of the whole conveyor, 25% ~ 30% of the price of the whole conveyor, and it is the primary part of daily management, protection, and replacement. The planning and selection of roller have an important influence on the normal operation of the conveyor, stable work, power consumption, and the price of the whole conveyor. Especially in the case of high belt speed, the requirements of the roller are becoming more stringent.
As the main component of the conveyor, the roller has become more and more stringent with the advancement of belt speed. The primary factors affecting the high-speed operation of the roller are run-out value and rotation resistance value. When the roller is working at high speed, the sealing structure of the roller will be affected by heat and other reasons. The structure planning of a high-speed roller is proposed in this paper.
1. Sealing structure of roller
The sealing structure is an important factor affecting the operating life and working resistance of the roller. There are two main methods for the sealing structure of rollers on the market:
(1) Non-touch seal (such as labyrinth seal). The working resistance of this kind of sealing is small, but due to the existence of internal conflict when working at high speed, it will inevitably lead to the occurrence of heat. With the change of air pressure, dust particles enter the bearing seal cavity along with the inhalation process, causing the bearing to work in a state of interference conflict, and aggravating the wear of the bearing.
(2) Touch-type seal. The sealing effect is better than the non-touch type, but the working resistance is large. In the case of large temperature and pressure differences and uneven distribution, the elastic deformation of the sealing lip is also inconsistent, resulting in a poor sealing effect.
It is not ideal to add the sealing effect only by adding the number of sealing passages and sealing length. The labyrinth sealing structure of the first rotating gap is the key to dealing with the sealing problem, the gap problems, slime or water will flow into the internal labyrinth channel, causing the failure of the roller, such a maze number is meaningless.
The roller proposed in this paper adopts the composite structure of axial labyrinth seal and touch seal, and its characteristics are as follows:
(1) The number of sealing passages of the axial labyrinth seal is not affected by the radial scale of the bearing and can be added appropriately. The sealing surface of the axial labyrinth is in the same direction as the centrifugal force of the water flow. The water that has entered the
seal when the roller rotates will flow to the top of the labyrinth along the sealing surface under the effect of centrifugal force. In order to enhance the effect, the top of the inner sealing ring can be considered to choose the circular arc structure.
(2) Add a sealing ring on the outermost side of the labyrinth seal to form a touch seal, which can not only deal with the "breathing problem" of the labyrinth seal but also won't add the depth of the bearing seat like other composite seal structures. Sealing ring NBR/PA6 material is lightweight, and corrosion resistant, and the friction coefficient is smaller than other engineering plastics.
(3) add a convex ring to the inner baffle ring (see Figure 1), and change the direction of axial movement when dust or water enters the gap of the inner baffle ring. When the roller works at high speed, a vacuum will be formed between the convex ring and the outer baffle ring to ensure the sealing effect.
2. Process characteristics and material selection
The radial run-out of the roller mainly depends on the radial error of the cylinder, the quality of the bearing seat, and the coaxiality of the assembly process. The radial run-out value of the roller has a great influence on the smooth work of the conveyor, especially when the radial run-out value is too large at high speed, the conveyor belt will oscillate violently and affect the normal work.
At present, most of the rollers are replaced by steel pipes, which are heavy in quality. The quality of the pipes, ovality, and outer diameter tolerances are not easy to guarantee, especially the existence of the discontinuity of the barrel structure affects the coaxiality, and it is easy to cause the rollers to be eccentric. Periodic vibration will occur due to the centrifugal force during the working process, which will affect the smooth operation of the conveyor belt.
3. Roller bearing selection
The working life of the roller mainly depends on the bearing and seal. Many idlers on the market use large-clearance bearings. Compared with ordinary bearings, large-clearance bearings have larger clears and ball diameters, which can reduce the sensitivity to coaxiality and enhance the ability to adapt to foreign objects.
However, the selection of bearings with large clearance will greatly affect the axial bearing capacity of the idler, especially after the belt speed is increased, the movement of the axial bearing capacity will cause the uneven working state of the belt conveyor. Even in severe times, it is necessary to stop the machine for debugging and overhauling from the beginning.
In this paper, we plan to select deep groove ball bearings with dust cover, which can not only ensure the cleanliness of the inside of the bearing, enhance the axial bearing capacity, reduce the frequent damage to the bearing caused by the axial high-frequency impact force, but also ensure the smooth function of the bearing extends the actual operating life of the bearing.
This paper has done some basic research on high-speed rollers from the aspects of structure, sealing, application, and technology of new materials. The roller adopts a composite sealing structure that combines an axial labyrinth and a touch labyrinth and uses a deep groove ball bearing with a dust cover. The application of new materials and the change of processing technology ensure the roller's rotating resistance, radial circular jumping, waterproof, dust-proof sealing, and other functions. Under the development direction of high-power, long-distance and large-throughput conveyors, the Roller structure proposed in this paper has little rotating resistance, low noise, and long operating life, which plays a vital role in the output power of the speed conveyor.
Global Conveyor Supplies Company Limited -RS series rollers
Shaft: Roller shaft is made of high precision cold drawn round steel, which has not been tempered and tempered. Precision chamfering milling machine and clamping ring grooving machine are used to process the shaft, so as to ensure that the axial displacement of the roller is almost zero.
Tube: Roller shaft is made of high precision cold drawn round steel, which has not been tempered and tempered. Roller shell adopts special frequency welding pipe, small bending degree, and small elasticity. Adopt advanced steel pipe chamfering cutting and inner hole machine tool, precision machining on both ends of steel pipe, effectively ensure the concentrically of the roller, minimize the machining error.
Bearing: Roller bearing adopts a special C3 deep groove ball bearing. Before assembly, the roller bearing has been filled with lithium grease and sealed permanently on both sides, which can realize lifelong maintenance free and prolong the service life of the bearing.
Seal assembly: The roller seal component is made of nylon material, and the structure form is a contact labyrinth seal structure. The inner and outer sealing form a high-precision labyrinth channel, the channel filled with long-term lithium grease so that the roller has good waterproof and dust-proof performance. Precision chamfering milling machine and clamping ring grooving machine are used to process the shaft, so as to ensure that the axial displacement of the roller is almost zero.
Bearing housing: The production of bearing housing adopts multi-stage precise automatic stamping molding to ensure the high precision of bearing and sealing position. Roller tubes and bearing housing at both ends 3mm full fillets are welded by carbon dioxide gas protection simultaneously with a dual gun automatic welding machine to provide a minimum of 70% penetration and ensure idling remains robust even under high loads and high speeds.
1. RS series rollers belong to GCS high-end conveying rollers.
2. The return/carrier/trough roller has a high-precision construction consisting of up to nine sealing parts, ensuring excellent water and dust resistance. With rubber or steel seals, multi-groove labyrinth seals.
3. The bearing housing and the roller tube are fully welded to ensure good contact throughout the roller. Grease is a permanent lubricant.
4. According to the customer's requirements, the surface of the roller can be painted with any color.
5. Material: Usually Q235 carbon steel (dedicated to conveying roller), A3 cold drawing shaft (can be higher precision according to different customer requirements).
6. Each roller will go through strict inspection and testing to ensure that each batch of rollers is truly high quality.
Please feel free to contact us to obtain conveyor rollers.
Post time: Dec-24-2021